DPDK mbufs contain a valid RSS hash only if PKT_RX_RSS_HASH is
set in 'ol_flags'. Otherwise the hash is garbage and doesn't
relate to the packet.
This fixes an issue with vhost, which, being a virtual NIC, doesn't
compute the hash.
Unfortunately the ixgbe vPMD doesn't set the PKT_RX_RSS_HASH, forcing
OVS to compute an hash is software. This has a significant impact on
performance (-30% throughput in a single flow setup) which can be
mitigated in the CPU supports crc32c instructions.
Reported-by: Dongjun <do...@dtdream.com>
Suggested-by: Flavio Leitner <f...@sysclose.org>
Signed-off-by: Daniele Di Proietto <diproiet...@vmware.com>
---
lib/dp-packet.h | 11 +++++++++++
lib/dpif-netdev.c | 2 +-
2 files changed, 12 insertions(+), 1 deletion(-)
diff --git a/lib/dp-packet.h b/lib/dp-packet.h
index e4c2593..6840750 100644
--- a/lib/dp-packet.h
+++ b/lib/dp-packet.h
@@ -529,11 +529,22 @@ dp_packet_set_rss_hash(struct dp_packet *p, uint32_t hash)
{
#ifdef DPDK_NETDEV
p->mbuf.hash.rss = hash;
+ p->mbuf.ol_flags |= PKT_RX_RSS_HASH;
#else
p->rss_hash = hash;
#endif
}
+static inline bool
+dp_packet_rss_valid(struct dp_packet *p)
+{
+#ifdef DPDK_NETDEV
+ return p->mbuf.ol_flags & PKT_RX_RSS_HASH;
+#else
+ return true;
+#endif
+}
+
#ifdef __cplusplus
}
#endif
diff --git a/lib/dpif-netdev.c b/lib/dpif-netdev.c
index f13169c..c4a4b3a 100644
--- a/lib/dpif-netdev.c
+++ b/lib/dpif-netdev.c
@@ -3036,7 +3036,7 @@ dpif_netdev_packet_get_rss_hash(struct dp_packet *packet,
{
uint32_t hash, recirc_depth;
- hash = dp_packet_get_rss_hash(packet);
+ hash = dp_packet_rss_valid(packet) ? dp_packet_get_rss_hash(packet) : 0;
if (OVS_UNLIKELY(!hash)) {
hash = miniflow_hash_5tuple(mf, 0);
dp_packet_set_rss_hash(packet, hash);
--
2.1.4
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